淮河流域土地利用变化对湖库水质的影响

湖库水体为我国主要的清洁饮用水源,系统解析湖库水质变化趋势及其主要原因,这对饮用水水源保护具有重要的现实意义。采用季节性Kendall趋势检验法对淮河流域14个湖库流域近8年(2003～2010年)水质变化趋势进行回顾性评估,并结合2000、2010年两期土地利用数据,进一步解析水质变化趋势与湖库流域土地利用变化的响应关系。结果表明,湖库水质与流域土地利用组成有关,流域的耕地、城镇用地等面积越大,水质越差,而林草地面积越大,湖库水质越好;14个湖库的COD、TP指标多为显著上升趋势,NH3-N指标上升和下降趋势参半;湖库水质的变化趋势与流域的土地利用变化相关,当耕地转变为城镇用地时,湖库水质趋势变化不明显;而当耕地转变为林地和湿地时,湖库的NH3-N、TP等水质指标有明显改善趋势。总体上,淮河流域湖库存在不同程度的污染问题,其中磷污染呈上升趋势。未来应加强土地利用管控,重视湖库水源地非点源污染的控制。

Impact of Water Quality in Lakes and Reservoirs under Land-use Changes in Huaihe River Basin

Lakes/reservoirs water body are the main clean drinking water resources. Analysis of water quality variation and its causes has important real significance to protect drinking water resources. The seasonal Mann-Kendall test was used to investigate the patterns of water quality trends of 14 lakes/reservoirs in Huaihe river basin based on long-term time series (2003-2010) of water quality data. According to the watershed land use data in 2000 and 2010, the relationship between water quality variation and land-use change was analyzed. The results show that water quality was related to the watershed land-uses. Higher percentages of the area in cropland and urban land were usually associated with the worse water quality, and higher percentages of the area in the forest and grassland were usually associated with better the water quality. More than 2/3 of the lakes and reservoirs show either significantly increasing or decreasing trends in COD, NH3N and TP, while only COD and TP increased for most of them. All of the water quality indicators were insensitive to the land use change when the cropland was converted into urban land. While the water quality indicators (such as NH3N and TP) seemed to be obviously improved if the cropland was converted into forest land and wetland. Overall, our historical assessment of water quality suggested that the water pollution of lakes/reservoirs in the Huaihe river basin have become an increasing issue. TP pollution appears up-ward trend. More management focuses should be given on the controls of land exploitation and agricultural non-point source pollution.